Abstract
Tea (Camellia sinensis ) and Camellia japonica belong to Theaceae. C. sinensis is one of the caffeine-containing plants, on the other hand, caffeine is not accumulated in C. japonica. The aim of this study is to clarify the reason why C. japonica is not purine alkaloid-producing species.
The caffeine biosynthetic pathway contains three S-adenosylmethionine(SAM)-dependent methylation steps. Caffeine synthase(TCS) , which is investigated by our group , is the SAM-dependent N-methyltransferase. TCS is involved in the last two steps(N-1 and N-3 methylation) of caffeine biosynthesis in tea leaves. First of all, we could show the presence of caffeine synthase homologous gene in C. japonica genome. The transcripts could be detected by RT-PCR, but not by northern blot analysis. We isolated two types of TCS homologous gene from C. japonica leaves by RACE. The identity of amino acid sequence between TCS homologous genes and TCS1 was 90% .
